System and Method for Operating a Large Single Engine Sweeper

ABSTRACT

A system and method for operating a large single engine sweeper includes a two-mode transfer case assembly inserted into the chassis drive train of the vehicle on which a package of sweeping equipment is mounted. In road mode operation, power from the chassis engine passes through a chassis automatic transmission, through a two-mode transfer case assembly to the differential and real wheel assembly. In sweep mode, power passes from a propel hydraulic motor into the two-mode transfer case assembly and then to the differential and real wheel assembly.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.13/466,532, filed on May 8, 2012, entitled “System and Method forOperating a Large Single Engine Sweeper” and claims the benefit ofProvisional U.S. Patent Application Ser. No. 61/614,949, filed Mar. 23,2012, entitled “Large Single Engine Sweeper”.

STATEMENT REGARDING FEDERALLY FUNDED RESEARCH AND DEVELOPMENT

The invention described in this patent application was not the subjectof federally sponsored research or development.

FIELD

The present invention relates to the engine power control system for alarge single engine sweeper.

BACKGROUND

Powered mechanical sweepers typically come in three sizes. The smallestsize is used for sweeping sidewalks and factory floors. Operators ofsmall sweepers may either walk behind the sweeper or ride on a smallseat positioned behind the sweeping mechanism. Medium size sweepers areused for cleaning parking lots and small roads such as private roads orlong driveways. Large sweepers are typically found on large public roadsor on vast expanses of concrete surfaces such as found in commercialairports.

A medium size sweeper is one in which the sweeper is either pulledbehind a tractor or where the sweeping equipment is mounted on thechassis of a small truck. The operator of a medium size sweeper willtravel at road speeds to the location to be swept. Once at the locationto be swept, the operator of the medium size sweeper engages thesweeping mechanism. With the sweeping mechanism engaged, the operator ofthe medium size sweeper uses the engine and transmission of either thetractor or small truck to control both the direction (forward andreverse) and speed of the sweeper when passing back and forth over thearea to be swept. Speed control of the medium size sweeper over thesurface being swept is typically accomplished by the foot pressureapplied by the operator of the sweeper on the accelerator pedal or thefoot brake to slow the sweeping vehicle using an automotive typefriction braking system.

A large size powered sweeper typically includes a dedicated or modifiedtruck chassis. However, the size of the areas to be swept, along withthe type and quantity of debris expected to be encountered, necessitatethe use of large brooms, large fans, and the capacity for picking uplarge pieces of debris along with a debris body for transporting a largeamount of swept-up debris. One example of such a large sweeper is theVacAll™ Legacy model sweeper which is manufactured and marketed by theGradall Division of the Alamo Group, the assignee of this U.S. PatentApplication.

Because of the size of a large sweeper, as distinguished from a mediumsize sweeper, and the additional power needed to operate the sweepingequipment on large sweepers, prior art large sweepers have typicallyincluded two internal combustion engines. One internal combustion engineis the truck chassis engine. As on the medium size sweepers describedabove, the truck chassis engine is always mechanically connected to thechassis drive train. As will be well understood by those of ordinaryskill in the art, attached to the chassis engine is a chassistransmission; typically, an automatic transmission. The chassisautomatic transmission is connected by a driveshaft to the chassisdifferential and a rear wheel drive assembly. The chassis differentialand the rear wheel assembly provide the power necessary to turn the rearwheels. The rear wheels propel the large sweeper to travel both at roadspeed to the location to be swept and then at sweeping speed over thesurface being swept. Thus, whether traveling along a highway or workingat a location that needs to be swept, the input by the operator of thesweeper to change the ground speed of the sweeper is by both placingfoot pressure on the accelerator pedal to control the engine rpm and theselection of the gear in the chassis automatic transmission.

The second internal combustion engine in a large sweeper, typicallyreferred to as an auxiliary engine, is usually mounted on the vehiclechassis behind the driver's compartment. This second internal combustionengine provides power to the sweeping equipment. When the large sweeperarrives at the large area, runway or road to be swept, the secondinternal combustion engine is put into operation. The operator of thevehicle with the sweeping equipment mounted thereon then drives thevehicle at a slow speed over the area to be swept.

The chassis internal combustion engine that comes with the vehiclechassis is used to propel large prior art sweepers using the chassisdrive train. In some prior art sweepers, the sweeper moves too fast overthe surface being swept. Accordingly, the operator of the sweeper mustcontrol the speed of the sweeper by maintaining continuous variablepressure on the brake pedal.

The second internal combustion engine is used to provide the powerneeded to operate all of the sweeping mechanisms. Unlike the chassisinternal combustion engine, the second internal combustion enginetypically bears an EPA rating as an off-road engine. The second internalcombustion engine typically has its own cooling and air intake systems.The fuel tank and batteries for the second internal combustion engineare typically shared with the chassis internal combustion engine.Controls available to the operator provide for operating the variablespeed broom motors and some of the sweeping functions; however, mosteverything regarding the sweeping operation runs at a speed directlyproportional to the speed of the second internal combustion engine.

The disadvantages of operating a large sweeper having two internalcombustion engines are the large amount of fuel consumed from theoperation of two internal combustion engines, the wear and associatedmaintenance required to keep two internal combustion engines inoperating condition as opposed to one internal combustion engine, andthe noise and vibration from two internal combustion engines. Such noiseand vibration has been shown to result in driver fatigue. In addition,since the brakes which are part of the vehicle chassis assembly are usedto control the speed of the large sweeper in sweep mode, more frequentreplacement of the brake pads, brake drums, or brake rotors on the wheelbrakes is required.

Accordingly, there is a need for a large sweeper that reduces fuelconsumption, reduces wear and maintenance, reduces noise and vibration,and does not require frequent replacement of parts of the wheel brakeassemblies.

Attempts have been made to create a street cleaning vehicle with asingle engine. One such example is shown in U.S. Pat. No. 6,073,720 toVanderlinden. Therein, a power take-off from the chassis transmission isconnected to a hydraulic pump. The hydraulic pump is connected to ahydraulic motor which is mounted on and is mechanically connected to therear chassis differential. Power from the single chassis engine is alsoused to drive the sweeping equipment mounted on the chassis of thevehicle. Those of ordinary skill in the art will understand that thesystem disclosed in U.S. Pat. No. 6,073,720 to Vanderlinden requiresmodifying the chassis transmission and the rear chassis differential.Such modification of chassis components by a sweeper manufacturer isboth expensive and typically voids the warranty on the chassis drivesystem components by the manufacturer of the vehicle chassis assembly.Because of these problems, the single engine sweeper proposed in U.S.Pat. No. 6,073,720 by Vanderlinden has not been generally accepted bythe sweeper industry in the United States.

Thus, the need still remains in the art for a large sweeper having asingle internal combustion engine. Those of ordinary skill in the artwill understand that as more demands are put on a single internalcombustion engine in a large sweeper, more control inputs are requiredof the vehicle operator to manage both the distribution of power betweenthe vehicle and the sweeping equipment while guiding and controlling thespeed and the direction of the large sweeper over the large area to beswept. Accordingly, there is an additional need to retain all of theadvantages of a large vehicle chassis when not sweeping and to provide aseparate system for controlling the speed of the vehicle when sweeping.

SUMMARY

The system and method for operating a large single engine sweeper of thepresent invention includes a two-mode transfer case inserted into thedrive train of the vehicle on which the sweeping equipment is mounted. Afront drive shaft extends from the rear of the chassis automatictransmission to the front side of the two-mode transfer case. A reardrive shaft extends from the back side of the two-mode transfer case tothe chassis differential and rear wheel drive assembly.

In travel mode, power from the chassis engine passes from the chassisengine through the chassis automatic transmission, through the two-modetransfer case and to the chassis differential and rear wheel driveassembly. The two-mode transfer case acts effectively as if it is notthere in travel mode as it performs no mechanical function.

In sweep mode, power passes from the chassis engine from the chassisautomatic transmission to the front side of the two-mode transfer case.The gear trains within the two-mode transfer case are set so that torqueinput from the chassis engine through the automatic transmission nolonger passes directly through the two-mode transfer case. Rather, thetorque to the front of the two-mode transfer case provides the necessarytorque to operate the hydraulic pumps which provide hydraulic fluid tothe hydraulic motors and hydraulic cylinders used with the sweepingequipment. This interruption of the flow of mechanical power transformsthe nature of the vehicle. Specifically, torque no longer follows adirect path from the chassis engine to the rear wheels.

At the same time that the flow of mechanical power from the chassisengine to the rear wheels is interrupted, the two-mode transfer case nowprovides mechanical power to a hydraulic propel pump. The hydraulicpropel pump provides a power input to the hydraulic propel motor mountedon the back side of the two-mode transfer case to a second gear trainwithin the two-mode transfer case. This second gear train within thetwo-mode transfer case provides a torque output to the rear drive shaftand then to the chassis differential.

Thus, when the large single engine sweeper is placed in sweep mode, theflow of mechanical power through the two-mode transfer case from thechassis automatic transmission is interrupted so that mechanical powerfrom the chassis automatic transmission no longer flows directly to thechassis differential and rear wheel drive assembly. Instead, themechanical power to the chassis differential and rear wheel driveassembly originates at the hydraulic propel pump and the hydraulicpropel motor and then passes into the two-mode transfer case. From thetwo-mode transfer case, the mechanical power provided from the propelhydraulic pump and the hydraulic propel motor turns the chassisdifferential and rear wheel drive assembly to move the sweeper acrossthe surface to be swept when in sweep mode.

When in sweep mode, the position of the accelerator pedal no longerprovides input to the system which controls the speed of operation ofthe chassis engine. Instead, in sweep mode, the chassis engine may beset at a predetermined speed and the movement of the accelerator pedalby the vehicle operator is now connected to another system whichcontrols the flow of hydraulic fluid from the propel hydraulic pump andis disconnected from the system which controls the rpm of the chassisengine. The flow of fluid from the propel hydraulic pump to the propelhydraulic motor then controls the speed of the large single enginesweeper instead of the engine speed. Thus, when sweeping, the operatorof the vehicle uses the accelerator; however, movement of theaccelerator pedal by the vehicle operator causes the speed of the largesingle engine sweeper to be controlled in an entirely different way.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A better understanding of the system and method for operating a largesingle engine sweeper may be had by reference to the drawing figures,wherein:

FIG. 1 is an exploded side elevational view of the large single enginesweeper of the present invention;

FIG. 2 shows a line representing the flow of power superimposed over thedrive train indicating the path taken by the power from the chassisengine when the large single engine sweeper is in road mode;

FIG. 3 shows a line representing the flow of power superimposed over thedrive train indicating the path taken by the power from the chassisengine when the large single engine sweeper is in sweep mode.

DESCRIPTION OF THE EMBODIMENTS

An exploded view of the large single engine sweeper 100 of the presentinvention appears at FIG. 1. The front portion of the vehicle includes acab 110 for the vehicle operator. The cab sits on the vehicle chassisassembly 120. As is known to those of ordinary skill in the art, thevehicle chassis assembly 120 includes a chassis engine 127 located nearthe vehicle operator's cab 110. A chassis automatic transmission 128 isattached to the chassis engine 127. The chassis engine 127, chassisautomatic transmission 128, and cab 110 for the vehicle operator sit onframe rails 122. The frame rails 122 extend behind the vehicleoperator's cab 110 to the rear drive wheels 124. A chassis driveshaftassembly 126 provides power to the rear drive wheels 124 through achassis differential and rear axle assembly 129. Most of themanufacturers of prior art sweepers purchase the rolling vehicle chassisassembly 120 and vehicle operator's cab 110, as shown in FIG. 1, from atruck manufacturer and then mount a free-standing sweeping equipmentpackage 130 powered by a second internal combustion engine on the framerails 122.

The sweeping equipment package 130 may include a large rotating broomand/or one or more gutter brooms 132. Located near the centerline of thevehicle chassis assembly 120 is a suction or vacuum head 134 for pickingup debris such as rocks, stones, bottles, pieces of asphalt, along withwet and dry leaves. A negative pressure at the suction or vacuum head134 results from the air flow created by a large fan (not shown). Thematerial picked up by the suction or vacuum head 134 passes into a largetiltable debris body 136. A hingedly mounted, hydraulically operatedtailgate 137 enables emptying the debris body 136. In some sweepers, anintake or pick up tube 138 is mounted on the back of the debris body 136and is used for manually picking up leaves or other types of debris.Many sweepers also include a water tank 140. Water from the water tank140 passes through a hydraulically powered water pump to a wand orsprayer to loosen debris dried on the surface being swept, as well asdust control.

All of the equipment in the sweeping equipment package 130, to includethe brooms, the fan creating the air flow which results in a negativepressure at the suction or vacuum head, and the water pump is operatedby hydraulic motors. The operating parts within the sweeping equipmentpackage 130 are positioned by the use of hydraulic cylinders. Thehydraulic fluid which enables the hydraulic motors to produce the neededrotational torque and the hydraulic cylinders to provide the neededlinear force comes from one or more hydraulic pumps.

In the disclosed invention, located about halfway between the vehicleoperator's cab 110 and the rear drive wheels 124 in FIG. 1 is a two-modetransfer case 20. The two-mode transfer case 20 receives rotationalpower from the chassis automatic transmission 128 through a front driveshaft 22. When the vehicle 100 is in road mode as shown in FIG. 2; thatis, traveling from one location to another between sweeping jobs, therotational power from the chassis automatic transmission 128 passesdirectly through the two-mode transfer case 20 to the chassisdifferential and rear axle assembly 129 via a rear drive shaft 24 wherethe rotational power is used to turn the rear drive wheels 124.

As shown in the schematic of FIG. 3, when the gears in the two-modetransfer case 20 are shifted from the first mode into the second mode,the two-mode transfer case 20 is then used to provide rotational powerto multiple hydraulic fluid pumps such as the fan hydraulic pump 26 andthe implement hydraulic pump 28 when the large single engine sweeper 100is in sweep mode. The fan hydraulic pump 26 on the left front of thetwo-mode transfer case 20 provides rotational power to a fan motor 30.The fan motor 30 turns the large suction fan which creates a negativepressure at the suction or vacuum head 134.

Another rotational power output from the two-mode transfer case 20provides rotational power to an implement hydraulic pump 28. Theimplement hydraulic pump 28 provides hydraulic fluid to the hydraulicmotors which turns the brushes and pumps the water, as well as the otherhydraulic motors and/or hydraulic cylinders which are used to move andposition the various operating parts of the sweeper equipment.

Shown on the right rear of the two-mode transfer case 20 in FIG. 3 isthe propel hydraulic pump 32. The propel hydraulic pump 32 provideshydraulic fluid to a propel hydraulic motor 34. The rotational powerfrom the propel hydraulic motor 34 passes back into the transfer caseassembly 20. The propel hydraulic motor 34 is mechanically connected tothe rear drive shaft 24 within the two-mode transfer case 20. Thus, insweep mode, it is the propel hydraulic motor 34 which is mechanicallyconnected to the differential and rear axle assembly 129 by the reardrive shaft 24 and causes the rear drive wheels 124 to rotate.

When the large single engine sweeper 100 is in sweep mode, no rotationalpower from the chassis engine 127 passes directly through the two-modetransfer case 20 to turn the rear drive wheels 124. Instead, therotational power from the chassis automatic transmission 128 goes to thetwo-mode transfer case 20 to operate the hydraulic propel pump 32 alongwith the other hydraulic pumps. Hydraulic fluid from the hydraulicpropel pump 32 goes to the hydraulic propel motor 34. Rotational powerfrom the hydraulic propel motor 34 goes back into the two-mode transfercase 20. The rotational power from the hydraulic propel motor 34 thatgoes back into the two-mode transfer case 20 is used to turn the reardrive shaft 24 which connects the two-mode transfer case 20 to thechassis differential and rear axle assembly 129. When in sweep mode, allof the power used to propel the sweeper 100 forward is received from thehydraulic propel motor 34.

Operation

The large single engine sweeper 100, according to the present invention,is driven in road or travel mode to a location where sweeping is to takeplace. Power from the chassis engine 127 passes through the chassistransmission 128 to the two-mode transfer case 20. From the two-modetransfer case 20, the rotational power passes to the chassisdifferential and rear axle assembly 129 to power the rear drive wheels124.

When the large single engine sweeper 100 arrives at the location to beswept, the single engine large sweeper 100 is ready to be placed insweep mode.

Placing the large single engine sweeper 100 in sweep mode requires thatthe operator of the large single engine sweeper 100 bring the vehicle to(a) a full stop, (b) shift the chassis automatic transmission 128 intoNeutral, and (c) set the parking brake 144 located within the vehicleoperator's cab 110. The sweep mode is now engaged by the operator of thelarge single engine sweeper 100 by pressing a button on the controlpanel 140 which operates the engine power control system of the presentinvention. With the sweep mode engaged, the chassis automatictransmission 128 is placed into Drive. Shifting the chassis automatictransmission 128 out of Drive will disengage the sweep mode.

In sweep mode, the two-mode transfer case 20 provides rotational powerto all of the hydraulic pumps which supply hydraulic fluid to thehydraulic motors and to the hydraulic cylinders found in the sweepingequipment package 130. In addition, the flow of rotational power fromthe chassis automatic transmission 128 through the two-mode transfercase 20 to the chassis differential and rear axle assembly 129 isinterrupted at the two-mode transfer case 20. Instead, the two-modetransfer case 20 receives power from the hydraulic propel motor 34. Thispower from the hydraulic propel motor 34 passes through the rear driveshaft 24 between the two-mode transfer case 20 and the chassisdifferential and rear axle assembly 129.

When the vehicle operator places the single engine sweeper 100 in sweepmode by pressing on the button on the control panel 140, the chassisengine 127 is set to operate at a predetermined fixed rpm by the controlsystem. Once this predetermined fixed chassis engine rpm is set, itcannot be changed by the vehicle operator. Control over the forwardspeed of the large single engine sweeper now completely depends on theflow of hydraulic fluid from the propel hydraulic pump 32 to the propelhydraulic motor 34. In sweep mode, control of the flow of hydraulicfluid from the propel hydraulic pump 32 is controlled by the movement ofa swash plate in the propel hydraulic pump 32. The movement of the swashplate in the propel hydraulic pump 32 is controlled by an electronicsignal related to the position of the accelerator pedal 145. Theaccelerator pedal is the same pedal normally used to govern the speed ofthe chassis engine 127 when in road mode. When the driver pushes down onthe accelerator pedal, the output of hydraulic fluid from the propelhydraulic pump 32 increases, thereby causing the power output of thepropel hydraulic motor 43 to increase, and the large single enginesweeper 100 will move across the surface being swept at a faster speed.If the vehicle operator of the large single engine sweeper 100 reducesthe foot pressure on the accelerator pedal 145, the large single enginesweeper will slow down. If the operator removes all foot pressure fromthe accelerator pedal 145, the large single engine sweeper 100 will slowto a stop. If something were to happen to the vehicle operator of thelarge single engine sweeper 100, and assuming that the foot of thevehicle operator falls away from the accelerator pedal 145, the systemwill act like a dead-man control.

The vehicle operator can turn the speed limiter on and set the maximumtravel speed for the large single engine sweeper 100 depending on thevehicle operator's assessment of the area to be swept. With the speedlimiter on and set, fully depressing the accelerator pedal 145 willachieve the pre-set maximum speed. As indicated above, if the operatorof the large single engine sweeper 100 reduces foot pressure from theaccelerator pedal, the large single engine sweeper 100 will slow downand eventually come to a stop. With or without the speed limiter on, theaccelerator pedal position is proportional to the speed of the largesingle engine sweeper 100. With the speed limiter on, the large singleengine sweeper 100 will move from zero (vehicle operator's foot off theaccelerator pedal 145) to the pre-set maximum speed on the speed limiter(accelerator pedal 145 fully depressed). And, as indicated above, ifsomething were to happen to the vehicle operator, the large singleengine sweeper 100 will come to a stop assuming that the foot of thevehicle operator falls away from the accelerator pedal 145. Thus, thesystem acts like a dead-man switch deactivating the hydraulicallyoperated propel system after a short pre-set period of time. The maximumspeed of the large single engine sweeper 100 while the speed limiter isengaged can be either changed or disengaged whether the large singleengine sweeper 100 is moving and whether or not the accelerator pedal145 is depressed.

Because of the increased ability of the vehicle operator to selectivelycontrol the speed of the large single engine sweeper 100 in sweep mode,there is little reason to use the brakes to control the speed of thelarge single engine sweeper 100 except for emergency stops or holdingthe large single engine sweeper 100 in position on a grade. In addition,the continuous input of foot pressure on the accelerator pedal 145protects the vehicle operator in the case of an event where the vehicleoperator is no longer able to operate the large single engine sweeper100. When foot pressure is taken off the accelerator pedal 145, thelarge single engine sweeper 100 will come to a stop, and the propelsystem becomes deactivated after a short pre-set period of time.

When the sweeping job has been completed, the large single enginesweeper 100, while still in sweep mode, is brought to a stop. Bypressing the auto store button on the control panel 140, everything thatwas running in the sweeper equipment package 130 is shut off and thesweeper equipment package 130 is put in the storage location. Theparking brake 144 is set by the vehicle operator and the chassisautomatic transmission 128 is shifted into Neutral. A toggle switch onthe control panel 140 is labeled “road mode” on the top and “sweep mode”on the bottom. The operator may now press the “road mode” button. Thetwo-mode transfer case 20 shifts after the parking brake 144 is set andthe chassis automatic transmission 128 is placed in Neutral.

When the sweeping job has been completed, as indicate above, thesweeping equipment is positioned in its storage location for transportto another area to be swept.

The large single engine sweeper 100 is then taken out of sweep mode andplaced back into road mode. Rotational power from the chassis engine 127and chassis automatic transmission 128 now passes directly through thetwo-mode transfer case 20 to the chassis differential and rear axleassembly 129.

Those of ordinary skill in the art will understand that the engine powercontrol system of the disclosed invention provides several advantagesover large sweepers having two internal combustion engines, as follows.

1. Lowered exhaustion emissions and lower fuel consumption.

2. Quieter operation and less vibration because of lower engine speed.

3. Less maintenance and replacement of components subject to wear andless adjustment of engine components.

4. Less operating cost.

5. Accurate vehicle operator selected vehicle speed control and dynamichydraulic braking while in sweep mode from simply changing only theposition of the accelerator pedal in the vehicle operator's cab.

Those of ordinary skill in the art will also understand that while thepresent invention has been explained with regard to its use on a largesweeper, the disclosed invention may be adapted for use on smallersweepers.

What is claimed is:
 1. A large single engine sweeper operable in eithera road mode or a sweep mode, said large single engine sweeper includinga rolling vehicle chassis, said rolling vehicle chassis beingconstructed and arranged for the mounting and positioning of a chassisbrake system, a chassis engine, a chassis automatic transmissionconnected to said chassis engine, a front drive shaft connected to saidchassis transmission, a two-mode transfer case connected to said frontdrive shaft, a rear drive shaft connected to said two-mode transfercase, and a chassis differential and rear wheel drive assembly attachedto said rear drive shaft along with a debris pick-up and picked-updebris containment system mounted on said rolling vehicle chassis, saidchassis engine speed being controlled by the position of a variableposition accelerator pedal when the large single engine sweeper is inroad mode, said large single engine comprising: a propel hydraulic pumpand propel hydraulic motor combination constructed and arranged toreceive mechanical torque from the two-mode transfer case in the sweepmode; said propel hydraulic motor constructed and arranged to providemechanical torque to said two-mode transfer case for moving the largesingle engine sweeper in the sweep mode; means for controlling thehydraulic fluid output of said propel hydraulic pump to said propelhydraulic motor using the variable position accelerator pedal when thelarge single engine sweeper is in sweep mode; whereby in the sweep mode,said variable position accelerator pedal is disconnected from thechassis engine speed control and connected to said propel hydraulic pumpto control the flow of hydraulic fluid to said propel hydraulic motorand when returned to the road mode, the variable position acceleratorpedal is disconnected from said propel hydraulic pump and reconnected tothe chassis engine speed control.
 2. The large single engine sweeper asdefined in claim 1 wherein said chassis engine operates at apredetermined rpm in the sweep mode.
 3. The large single engine sweeperas defined in claim 1 wherein said chassis transmission operates in apredetermined gear range in the sweep mode.
 4. The large single enginesweeper as defined in claim 1 wherein the speed of the chassisdifferential and rear wheel drive in the sweep mode is dependent on theoutput of mechanical torque from the propel hydraulic motor to thetwo-mode transfer case and from the two-mode transfer case to the reardrive shaft.
 5. The large single engine sweeper as defined in claim 1wherein the variable position accelerator pedal is used to control theposition of a swash plate in the propel hydraulic pump which controlsthe flow of hydraulic fluid from the propel hydraulic pump to the propelhydraulic motor.
 6. The large single engine sweeper system as defined inclaim 1 wherein the speed of the large single engine sweeper in thesweep mode may be varied from zero to a predetermined maximum speed byvarying the position of the variable position accelerator pedal.
 7. Thelarge single engine sweeper as defined in claim 1 wherein the speed ofthe vehicle in sweep mode when the accelerator pedal is fully depressedis set by the vehicle operator.
 8. The large single engine sweeper asdefined in claim 1 wherein the chassis brake system is used only in theevent of an emergency stop or to hold the position of the large singleengine sweeper on a grade when the large single engine sweeper is in thesweep mode.
 9. The large single engine sweeper system as defined inclaim 6 wherein the predetermined maximum speed of the large singleengine sweeper in the sweep mode is determined by the vehicle operator.10. The large single engine sweeper as defined in claim 8 wherein thethe large single engine sweeper will reach the predetermined maximumspeed when the variable position accelerator pedal is fully depressed.11. The large single engine sweeper as defined in claim 1 will exit thesweep mode if the variable position accelerator pedal is not depressedfor a predetermined period of time.